Synthetization of Refractory/Transition Metal Diboride & Carbide Precursors for Chemical Vapor Infiltration (CVI) of Ceramic Composites

Navy STTR 24.A - Topic N24A-T021
ONR - Office of Naval Research
Pre-release 11/29/23   Opens to accept proposals 1/03/24   Now Closes 2/21/24 12:00pm ET    [ View Q&A ]

N24A-T021 TITLE: Synthetization of Refractory/Transition Metal Diboride & Carbide Precursors for Chemical Vapor Infiltration (CVI) of Ceramic Composites


OBJECTIVE: Develop a stable, scalable synthesis route for a refractory diboride precursor suitable for evaporation in a Chemical Vapor Infiltration (CVI) system.

DESCRIPTION: Properties of refractory/transition metal diborides have attractive coating options for extreme applications with melting temperatures above 3200C, high hardness, and excellent thermal oxidation resistance. Metal diborides such as hafnium, zirconium, tantalum, iridium, etc. have no commercially available single source CVI precursor. Depositing metal diboride via chemical vapor deposition routes such as CVI offer a viable method of integration into Ceramic Matrix Composite (CMCs) with respect to protective interface coatings. Commercial availability of refractory metal boride precursors to support epitaxial deposition is non-existent and development efforts are scarce. This STTR topic aims to develop stable, repeatable and scalable routes for new precursors for integration into existing large scale CVI systems. This research is critical for domestic development of key precursors identified to have the potential for significant advancements in Ultra High Temperature CMC processing.

PHASE I: Demonstrate synthesis route and basic precursor properties (vapor pressure, melting/freezing temperature, density, etc.) using modeling, characterization and experimentation. Determine repeatable and projected scalability of formulation.

PHASE II: Optimize process and demonstrate repeatability. Determine projected scalability of compound formulation. Begin Chemical Vapor Deposition (CVD) deposition studies. Evaluate deposition temperature range for amorphous and crystalline coatings and associated data showing crystallinity, grain size and stoichiometry. Initiate infiltration studies.

PHASE III DUAL USE APPLICATIONS: Continue infiltration studies, modelling the infiltration process to determine optimal conditions (T, P, flow) to optimize densification of fiber preforms. Determine methods and measures to ensure reproducibility for scaling to larger preform sizes. Dual use activities could include commercial access to space components, as well as other high temperature applications in the energy and materials processing communities.


  1. Coltelli, Maria Beatrice and Lazzeri, Andrea. "Chemical vapour infiltration of composites and their applications." Chemical Vapour Deposition (CVD): Advances, Technology and Applications, CRC Press, July 2019, p. 363.
  2. Aguirre, Trevor G.; Lamm, Benjamin W.; Corson L. Cramer, Corson L. and Mitchell, David J. "Zirconium-diboride silicon-carbide composites: A review." Ceramics International, Volume 48, Issue 6, 15 March 2022, pp. 7344-7361.

KEYWORDS: Precursors, coatings, chemical vapor deposition, chemical vapor deposition, organometallics, ceramic matrix composites


The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 24.A STTR BAA. Please see the official DoD Topic website at for any updates.

The DoD issued its Navy 24.A STTR Topics pre-release on November 28, 2023 which opens to receive proposals on January 3, 2024, and now closes February 21, (12:00pm ET).

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Topic Q & A

1/24/24  Q. My main question is what you see as the most significant technical hurdle. Several CVI diboride precursors are known in the literature. Do you see them as having fundamental technical flaws? Or, do you see the challenge as more about being able to controllably synthesize and scale up those or similar precursors? Any insight you can provide, would be greatly appreciated.
   A. There are some flaws with some of the precursors mentioned in old literature. If investigated, these flaws should be addressed. Development of new precursors that avoid these issues would also be of interest.
1/24/24  Q. My second question is about transition. Is this topic geared more toward a general capability to support future development, or are there specific platforms with a significant near-term need?
   A. We are not interested in transition at this Phase of the topic. We are more interested in pushing the technology and general capabilities forward. If you are looking for a specific direction to go in for transition, it may be worth reaching out to a prime contractor to see if there is any interest.
1/4/24  Q. 1. CVI on what type of fibers needed? (Carbon Nano Fibers) ok?
2. Oriented Fibers or any direction oriented is ok?
3. DOD will proved Fibers for coatings?
   A. This STTR is looking for development of the precursors for CVI not necessarily the composites themselves. We want the focus on the development of UHTC precursors. The end application is for composite development, but is not expected to be the initial priority in early phases.

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